This invention relates to image sensors, particularly of the type comprising an array of pixels, and each pixel including a photo-responsive diode. The invention also relates to a method of manufacturing such an image sensor.
There is currently much interest in reducing the manufacturing complexity of an image sensor array. For example, an improved yield is obtained if the number of processing steps required for the manufacture of the array is reduced. In the case of an array of pixels formed using thin-film technology, the number of accurate masks which are required in the manufacturing process is of particular importance.
These issues have lead to an interest in diode-based pixel configurations. For example, a known pixel configuration comprises a photodiode and a switching diode in series between respective row and column conductors. There have also been proposals to fabricate a stacked pixel configuration, such as shown in U.S. Pat. No. 4,797,560 which simplifies the mask patterns, and enables a high resolution image sensor to be fabricated.
One problem encountered with thin film diodes is the edge leakage current between the n-type semiconductor and p-type semiconductor material across the edge of the diode structure. This leakage current becomes increasingly significant as the dimensions of the individual pixels are reduced.
This invention seeks to reduce further the complexity of manufacturing a diode-based image sensor array, and also seeks to address the problem of edge leakage current effects in thin film diodes.